Wattage controlling system



1 1949- L. F. BHIRD 2,470,460

WAT'fAGE CONTROLLING SYSTEM Filed June 5. 1948 k 0 3n 2 k? :4 rnve I IN VEN TOR.

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. 4657' F. 5/20 15 'Pe/MMY V01. 7465 BY RNEY 2 Patented May 17, 1949 WATTAGE CONTROLLING SYSTEM Lester F. Bird, Newark, N. J assignor to Hanovia Chemical and Mfg. Company, Newark, N. 5., a

corporation of New Jersey Application June 5, 1948, Serial No. 31,241

Claims.

The present; invention relates to a Wattage controlling system and more particularly to an automatic wattage controlling system and transformer therefor.

It is a well recognized practice to wind a primary coil and a secondary coil of a transformer, e. g. a transformer of the high reactance type, in such manner that the primary coil and secondary coil are physically separated and magnetically loosely coupled on a core having a magnetic leakage shunt between the primary and secondary windings. Such transformers are usually employed to operate devices, e. g. metal vapor arc lamps or discharge tubes, which require a secondary reactance to limit the current that will flow from the transformer secondary to any resistance load between a short circuit condition and the maximum input of, for example, an arc lamp. The design of the transformer usually provides for starting currents of about 1.45 times the usual operating currents and during operation the voltage across the transformer secondary is equal to the voltage across the lamp itself. The reactance of th transformer secondary serves to stabilize the arc lamp and keep it lighted. Suchreactance is inductive in character and the current in the lamp circuit lags, the induced secondary voltage causing a lagging power factor for the supply currents. With such a transformer, the wattage consumed by the lamp varies approximately as the square of the percentage change of line voltag supply, e. g. a percent change in line voltage results in a 21 percent change in lamp wattage. Fluctuations in line supply voltages, therefore, result in wide variatlons in the light output of the lamp and continuous readjustment of the input connections is required on the transformer if the lamp wattage is to be maintained at or near a constant value.

With the development of ultraviolet lamps, wide fields, or important fields and critical field of use, have been opened in which uninterrupted irradiation over an extended period of time within critical radiation output limits is essential. Therefore, with respect to radiation output limits, a constant wattage operated lamp is important, and a transformer system which may be so regulated as to automatically control wattage outputs under variable input voltages is highly desirable,

- since only thereby is it possible to provide a substantially constant wattage input to the lamp within such limits of constancy that a reasonably controlled radiation output at the desired level is obtained. A conventional transformer which is not capable of providing a wattage output substantially independent of fluctuations in line voltages may deleteriously affect the desired irradiation essential in some processes. For example, if the line voltage varies from 200 to 250 volts, the change in secondary wattage, the wattage consumed by the lamp, would generally be of the order of 2000 to 3000 watts. Such a wide variation may, therefore, be beyond the ability of the lamp electrodes to carry, and may result in the extinction of the lamp or destruction of the electrodes. The resultant variations in wattage reflected from variable voltages would change the light intensity and when this condition exists, for example, in printing processes, it would result in either an over-exposure or an under-exposure. A similar disadvantageous condition would prevail in processes involving the irradiation of liquids, etc. Also, when a lamp, e. g. a mercury vapor arc lamp, is once extinguished due to its inability to cope with large variations in wattage, it would require a waiting period before being capable of rte-ignition and the more often such a lamp is restarted the shorter becomes its useful life.

It is one object of this invention to provide an automatic wattage control for operation with an arc lamp or vapor discharge device which supplies means for stabilizing a lamp, etc", by at capacitatlve reactance. It is another object of this invention to provide a transformer which has a highly emcient performance and which permits economies in material and current. It is a further object of this invention to provide a transformer capable of operation under various line supply voltages. It is a still further object of this invention to provide a transformer which permits the secondary circuit to operate at optimum value substantially independent of variations in line input voltages. Other objects and advantages of this invention will become apparent from the description hereinafter following and the accompanying drawings forming part hereof, in which:

Figure 1 illustrates a. diagrammatic representation of the transformer according to the invention,

Figure 2 illustrates schematically the transformer of the invention and circuit therefor, and

Figure 3 graphically illustrates an advantage of the invention.

The automatic wattage controlling transformer of the present invention operates most eillciently with a secondary load circuit which comprises means for stabilizing a lamp, etc., by

a capacitative reactance. Actually, it is inherently impossible to operate with only a seriescapacitor for the stabilizing means in the transformer system .of my invention because of an oscillating condition which follows the use of only series capacitativo reactance for lamp stabilization. Therefore, I utilize a resultant capacitative reactance produced by employing a suitable. capacitor in an effective series connection with an inductive reactance which, with the series capacitor chosen to be about twice the value of the inductive reactance, leaves a resultant capacitative reactance in the circuit. Since the resultant reactance is the one which provides stabilization for the lamp, and in this case is capacitative, the lamp is actually operating from a capacitative reactance and so the currents flowing in the secondary or lamp circuit are of leading power factor. By properly proportioning the coils of the transformer and the ratio of windings of the primary coil to secondary coil, the secondary circuit is reflected through the transformer to the primary circuit in such manner that the energy in the secondary circuit assumes a condition of high stability and is merely excited by the primary input.

The variations in the primary input voltage then no longer appear in equal or greater value in the secondary circuit but are actually reduced so that fluctuations in the secondary circuit are less than 5 percent of those in the primary circuit and the overall reactance between the primary and secondary circuit is greatly reduced or neutralized by the condensive reactance re- Q Junction with a secondary load comprising a series capacitor and," for example, an arc .lamp, has undesirable characteristics with respect to values of primary currents necessary for the economical operation of the transformer system. For example, when an arc lamp, etc., operates with a capacitative reactance, the current being of leading power factor, a strongly leading current from the line supply is necessary because the power factor of the load is normally reflected into the transformer primary and this, of course, requires a primary winding of appropriate size to cope with the required current from the line supply. In order to allow economies in material and current and still provide a highly eflicient transformer, I have departed from the usual practice of transformer construction and have provided a primary coil wound in two or more physically separated sections with magnetic leakage paths between them. My purposes in, doing this is to isolate the secondary magnetic structure farther from the inputline than would be possible with the normal primary winding and to provide an adjustable reactance available in the primary system for optimumpower factor operation. The primary reactance of my transformer can be readily adjusted by modification of the leakage shunt between the sections of primary windings and without appreciably affecting the leakage reactance between the primary and secondary windings.

Referring to the accompanying drawings,

Figure 1 illustrates an embodiment of my invention in diagrammaticform with sections of the split primary winding and a single secondary winding mounted on acore structure having leakage shunts built into the core structure. Thus, the magnetic core structure I contains leakage shunts 2 and 3 and has wound about it primary coil sections 4 and 5 with the primary leakage shunt 2 between them. The secondary coil 6 is likewise wound about the core structure and separated from the primary sections by the leakage shunt 3. I

In Figure 2, I have schematically shown the transformer windings with a secondary load comprising a capacitor 1 and an arc discharge lamp 8. The magnetic core structure 9, and leakage shunts l0 and II, the primary coil sections l2 and 13 and the secondary coil it, all correspond to similar components of Figure 1. The capacitor is chosen to have a reactance at the input frequency of about twice the reactance of the secondary of the transformer at rated load current. Since the capacitor is chosen to be about twice the value of the natural leakage reactance of the secondary winding [4 of the transformer, there is a leading power factor current flowing through the arc lamp and the whole secondary circuit when the lamp is lighted. The power factor of this kind of load would normally be reflected into the primary of the transformer to require a strongly leading current from the line supply. However, the introduction of inductive reactance into the primary winding has a corrective effect on the power factor of the transformer system and so produces an improvement in power factor on the line supply circuit i5. This result follows because in such case the inductive reactance of the primary subtracts efiectively from the reflected condensive reactance of the secondary and results in a power overall reactancefor the system. This reduction in reactance improves the power factor of the input current and so produces 'a reduction in it. The primary current in any alternating current system is always at a minimum when the power factor is close to unity or at its highest value.

The reactance of the secondary winding of the transformer is not a fixed quantity, but is a variable dependent upon the current in the secondary coil, the flux density in the core, and the current in the primary winding. In general, the secondary reactance is greater at a lower flux density and lower at .greater flux density. The secondary reactance operates in series with the capacitor in the lamp circuit and since control of the lamp wattage is dependent upon the reactance in series with the lamp, any change in the overall circuit reactance affects the lamp wattage. An increase in overall reactance will reduce the lamp wattage and a reduction in overall reactance will increase the lamp Wattage. Therefore, in a circuit as illustrated in Figure 2, with the inductive reactance and capacitative reactance in series, the different reactances subtract from each other in such manner that if they were equal the Overall reactance of the secondary would become zero. For example, if the capacitor reactance is about ohms and the secondary inductive reactance is about 50 ohms, the overall reactance is the difference between them or 50 ohms capacitative. This is the overall reactance which functions to stabilize the lamp. If the inductive reactance increases to 55 ohms, the overall reactance is reduced to 45 ohms, etc. An increase in inductlve reactance, therefore, results in a reduction of overall reactance and a reduction in inductive reactance results in increased overall reactance.

Variable conditions for a normally operating lamp are almost always concerned with variable input voltages. With fixed reactances in the lamp system, the lamp wattage varies greatly with changes in line input voltages. With adjustable reactances the variations due to line voltage changes can be eliminated and when the adjustment of reactance can be made automatic with line voltage changes the lamp wattages can become independent of line input voltages. Such a result is found in the transformer of my invention because the changes in input voltage automatically bring about alterations in the transformer secondary reactance to eliminate to a major extent the variations in wattage which would ordinarily follow such a voltage change. There can be an increase in primary voltage which causes an increase in the flux density in the magnetic core structure, which in turn reduces the inductive reactance of the secondary coil and so increases the overall secondary reactance due to the difference between. the normal The reduction in primary current brought about by the application of my invention, therefore, reduces the primary currents by very desirable amounts and so provides a very worthwhile saving in the size of the wire necessary to carry these currents and, therefore, reduced magnetic core structures.

Having provided the transformer of this invention, I may utilize its benefits practically in any field where constant wattage input for lamps, etc., is desired. For example, the transformer of my invention may be utilized for high pressure mercury vapor lamps, incandescent lamps, high voltage discharge tubes, whether hot or cold cathode tubes, low pressure mercury lamps, such as fluorescent lamps or bactericidal lamps. It may also be used for plating processes, furnaces, and f0" processes involving the use of nnotocells.

What I claim is:

l. A wattage controlling system comprising in combination, a transformer having a magnetic core structure and mounted thereon a primary current input system comprising a plurality of coils in spaced relation to each other with high reluctance magnetic shunts between them, a secondary coil system mounted on said magnetic core structure in spaced relation to the primary coils with a high reluctance magnetic shunt between the said primary coils and the secondary coil system, a stabilizing wattage control circuit comprising a capacitor connected between one of wattage regulation of the lamp and render the power consumption relatively steady and essentially independent of the variations in input voltage. If, however, the transformer is designed with a low flux density under the primary coil,

' such that the iron is operated normally considerably below the knee of the saturation curve, the variations in flux density in the core under the primary winding will affect the flux density in the remainder of the core less, and the control exercised over the secondary wattage will be considerably weakened. The exact flux density at which the iron under the primary, coil must be operated in order to secure the optimum control must be determined for each kind of iron.

The transformer of my invention, as heretofore described, has a structure such that the power factor of the primary currents can be at a maximum throughout a large portion of the operating voltage range. Without the structure as herein set forth, the power factor will be at a maximum at a voltage value above the voltage operating range. Both these conditions are illustrated in' Figure 3 where [6 indicates the range of primary voltage over which the system operates.

The curve I! shows the variations of-primary input current with primary voltage change for a transformer having a primary lumped in a single coil and indicates that the minimum current values lay outside of the voltage operating range and, consequently, the maximum power factor lays outside the range. The curve.|8, however, relates to a split primary winding having a high reluctance shunt between the primary coil sections and indicates the advantage of thetransformer of this invention by enabling minimum primary input currents and, therefore, maximum power factor to lay within the operating voltage range.

. between one of the terminals of th terminals of said secondary coil system and a load so that all the current delivered from the secondary transformer winding to the load passes therethrough, said capacitor having a reactance at line frequency of approximately twice that of the self-inductance of the transformer secondary.

2. A transformer in combination with a stabilizing wattage control circuit for discharge devices, comprising a magnetic core structure having mounted thereon a primary input current system comprising a plurality of coils in spaced relation to each other and having between them high reluctance magnetic shunts, a secondary coil system of substantial self-inductance mounted on said magnetic core structure in spaced relation to the primary coils with a high reluctance magnetic shunt between said primary coils and the secondary coil system, said stabilizing wattage control circuit comprising a capacitor connected between one of the terminals of said secondary coil system and a load so that all the current from the secondary transformer winding to the load passes therethrough, said capacitor having a reactance at line frequency of approximately twice that of the self-inductance of the transformer secondary.

3. A transformer in combination with a stabilizing wattage control circuit for discharge devices, comprising a magnetic core structure having mounted thereon a primary input current system comprising two coils in spaced relation to each other and having between them a high reluctance magnetic shunt, a secondary coil system of substantial self-inductance mounted on said magnetic core structure in spaced relation to the primary coils with a high reluctance magnetic shunt between said primary coils and the secondary coil system, said stabilizing wattage control circuit comprising a capacitor connected said secondary coil system and a load so that all the current from the secondary transformer winding to the load passes therethrough, said capacitor having a reactance 'at line frequency of approximately twice that of the self-inductance 01 the transformer secondary.

4. A transformer in combination with a stabilizing wattage control circuit for alternating current vapor arc lamps, comprising a magnetic core structure having mounted thereon a primary input current system comprising two coils in spaced relation to each other and having between them a high reluctance magnetic shunt, ar secondary coil system of substantial self-inductance mounted on said magnetic core structure in' spaced relation to the primary coils with a high I reluctance magnetic shunt between said primary coils and the secondary coil system, said stabilizing wattage control circuit comprising a capacitor connected between one of the terminals of said secondary coil system and a load .so that all the current from the secondary transformerwinding to the load passes therethrough, said capacitor having a reactance at line frequency of approximately twice that oi. the self-inductance oi the transformer secondary.

5. A transformer in combination with a stabilizing wattage control circuit for alternating current discharge tubes, comprising a magnetic core structure having mounted thereon a primary .input current system comprising two coils in spaced relation to each other and having between current from the secondary transformer winding to the load passes therethrough, said capacitor having a reactance at line frequency or approximately twice that of the self-inductance oi the transformer secondary.

IES'I'ER F. BIRD.

REFERENCES CITED The'rollowing references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 2,179,795 McCurtain Nov. 14, 1939 2,346,621 I Bola Apr. 11, 1944 1 

